The illustrative embodiments described in the present application are useful in systems including those for use in context aware environments and more particularly are useful in systems including those for determining location in a context aware environment.
The term responsive environment may be used to describe an environment that has computing capability and access to sensing technology data that allows the environment control to consider its current state or context and new events that occur that may change the state or context.
Context-aware environments typically utilize location information as an important type of context. Global Positioning System (GPS) devices are available that provide relatively reliable position determination functionality while outdoors. However, GPS signals are typically too weak to be effective indoors. Accordingly, the determination of indoor position is more problematic.
Over the last few years, several approaches to solve the indoor position determination problem have been attempted. Each of these traditional approaches places a certain amount of burden on the user. For example, in some systems, the user needs to proceed to a location at which the user presence can be sensed. In other systems, the user must wear a special device that interacts with the environment to indicate location.
In traditional indoor positioning systems, the location context is determined by one of a few known methods. In the simplest method, an indoor positioning system utilizes a field-of-view approach. With this method, objects have a means of identity and a means of communicating this identity when entering the field of view of the location-sensing apparatus. One of three traditional categories of systems may be utilized with this simple method. In one type of system, infrared location cones may be utilized. In those systems, the objects announce their identity using infrared signals. In a second type of system, video identification techniques may be used. In those systems, faces or unique markings are identified and associated with the viewed locations. In a third type of system, electro-magnetic field perturbations may be used. In those systems, objects carry tags that emit identification signals when present within the field. There, sensed objects are known to be within the location covered by the view of the sensing apparatus.
A second and slightly more complex method for determining location is based on radio frequency technology. In this method, objects carry an RF transmitter that can announce the identity of the object. The RF signal is detected at multiple RF receivers and the location is determined based on signal strengths across these receivers.
A third system for determining locations is based on ultrasonic signaling. In this method, objects carry a signaling device, often called a beacon. Signal detectors are placed throughout a room, and the location of the object is determined by triangulation among the detectors that receive the signal from the beaconing device. All of these indoor position determination methods are described in a paper entitled “Location of Mobile Devices Using Networked Surfaces,” by Hoffman and Scott, as presented at the 4rth International Conference on Ubiquitous Computing (UbiComp2002).
A fourth system integrating portions of the systems described above is described in a paper entitled “Location Estimation Indoors by Means of Small Computing Power Devices, Accelerometers, Magnetic Sensors, and Map Knowledge” by Vildjiounaite et. al., as presented at the First International Conference on Pervasive Computing in August of 2002. In that system, the user wears sensors that measure variables such as direction and speed. The sensors broadcast that information via RF signaling. A host computer receives the information and uses it to determine the location of the wearer. The location can be adjusted using traditional field-of-view approaches.
The first two methods described above have several deficiencies. For example, the object must be within a field such as an electromagnetic or visual/audio field. This is problematic for several reasons. First, humans prefer not to be subjected to a local, relatively high-power continuous RF field. Second, such fields need to be omnipresent with complete area coverage for these systems to work well. Third, if the fields are omni-present, people may perceive privacy concerns. While the third method described above does not suffer the same disadvantages of the first two methods, it does require that objects wear a device that is currently bulky and expensive.
Accordingly, among other things, the prior art does not provide a context-aware environment that can adequately determine position information.